text: Generators provide radiation shielding for transport and to minimize the extraction work done at the medical facility. A typical dose rate at 1 metre from Tc generator is 20–50 μSv/h during transport.
  These generators' output declines with time and must be replaced weekly, since the half-life of Mo is still only 66 hours. Since the half-life of the parent nuclide (Mo) is much longer than that of the daughter nuclide (Tc), 50% of equilibrium activity is reached within one daughter half-life, 75% within two daughter half-lives. Hence, removing the daughter nuclide (elution process) from the generator ("milking" the cow) is reasonably done as often as every 6 hours in a Mo/Tc generator.